Conventionally, as a method for producing resin fine particles, a suspension polymerization method is known. This method is a method for placing a water based medium with a dispersion stabilizer dissolved in a reaction vessel with an agitator, introducing a polymerizable monomer with a polymerization initiator dissolved while agitating, and heating, thereby obtaining resin fine particles. However, the particle size distribution of the resin fine particles obtained by the method is wide, so that a sorting operation such as classification is necessary for the application requiring the homogeneity of the particle size of a column filling material, a spacer, a toner, a material for a foamed product, or the like, and thus it is extremely complicated.
In contrast, Japanese Kokai Publication Sho-57-102905 discloses a method for crushing a polymerizable monomer flow having a laminar flow characteristic to small liquid droplets by applying mechanical vibration, moving the same to a polymerization vessel in a continuous phase, and polymerizing by heating. However, according to the apparatus disclosed in this method, since a plurality of polymerizable monomer openings are provided, it is actually difficult to discharge by the same flow amount from each of the openings, so that the flow amount irregularity is occurred. Thus, the liquid droplets split at the same mechanical frequency has irregularity in capacity, that is, in size. Therefore, according to the apparatus, since the split state cannot be grasped sufficiently, in the case where split failure is occurred, it is difficult to avoid the split failure so that the particle size homogeneity of the final resin fine particles is deteriorated. Moreover, since the apparatus has no mechanism for checking the liquid droplet production state or the liquid droplet particle size, even in the case where the particle size homogeneity is deteriorated by the production condition fluctuation or the like, the production is continued as it is, and thus there is a problem that the homogeneity of the resin fine particles to be obtained is poor.